ENERGY HARVESTING USINGRF MEMS

RICHU JOSE CYRIAC

M120128EC

MICROELECTRONICS & VLSI DESIGN NIT CALICUT

WINTER 2012

OUTLINE

Introduction Limitation of existing RF MEMS

Design Fabrication

Energy stored by RF MEMS Reliability issues Conclusion

INTRODUCTION

MEMS energy harvesting – a new alternative

Electro-magnetic MEMS, Electrostatic MEMS, Piezoelectric MEMS – low efficiency, scaling issues, high cost.

Proposed design – scalable and easily integrated in microsystems.

RF MEMS convert solar energy into charge, can achieve a better benefits than photovoltaic cell.

LIMITATIONS OF EXISTING

Photovoltaic cells and wind power harvesting have several technical barriers.

In solar cells, the inherent physical limits, the black body energy conversion loss, optical loss, and internal resistance prevent their efficiency from reaching >20%

By applying a photosensitive coating and transparent electrode, the electric charge can be generated and stored in the RF MEMS structure.

Click icon to add pictureNOVEL DESIGN

RF MEMS-DESIGN

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RF MEMS-FABRICATION

1. Co-planar waveguide deposition and lithography

2. Silicon dioxide and wet etching

3. Pattern Sacrificial Photoresist

RF MEMS-FABRICATION

4. Aluminum deposition and patterning of Aluminum Bridges

5. Removal of Sacrificial polymer

Microscopic view of RF MEMS

Click icon to add picture

ENERGY STORED BY RF MEMS

ENERGY STORED BY RF MEMS

Membrane overlap over the signal isolation layer - determines the maximum energy that can be stored per area of the RF MEMS.

C=0.3 pF (switch off), C= 1 pF (switch on)

A maximum charge of 35 pC was found to be stored and discharged per cycle per switch.

VCQ

RELIABILITY ISSUES

Mechanical failures such as creep and fatigue are not a big problem.

Electrostatic discharge-induced(ESD) failure.

ESD results in charge injection and charge trapping in the interface.

CONCLUSION

RF MEMS has potential applications for energy harvesting.

Potential application in wireless sensors application.

Free energy source is available maintenance-free throughout the lifetime of the application.

The pull down voltage of the RF MEMS was found to be 35V with a resonant-frequency of 25 MHz.

Reliability issues like ESD still remains.

REFERENCE

Energy Harvesting Using RF MEMS, Yunhan Huang, Ravi Doraiswami, Michael Osterman, and Michael Pecht, Electronic Components and Technology Conference 2010

THANK YOU